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'._ ' ~ • i <br />,1, <br />INTRODUCTION <br />This review of the practice of waste injection into Devonian-age <br />geological formations in Southwestern Ontario was conducted at the <br />request of the Ministry of the Environment. Part of the Ministry's <br />statutory function is to develop adequate controls to guide the siting, <br />construction, and operation of disposal wells so that natural resources <br />such as soil and water are protected. Industries that have used dis- <br />posal wells in southwestern Ontario include the oil and gas production <br />industry, the chemical manufacturing industry, and operators of under- <br />ground storage caverns. Due to the relatively shallow depth of the dis- <br />posal strata, and the occurrence of several events where the rock media <br />failed to contain the wastes when high wellhead pressures were applied, <br />there was a need to review the current status of the problem and to sum- <br />marize and evaluate the risks associated with continued use of this dis- <br />posal zone. The subject disposal intervals are part of the Devonian <br />Detroit River Group. Underground Resource Management, Inc. (URM}, in <br />association with Gartner Lee Associates, Limited (GLA) was retained to <br />provide this review document. <br />Subsurface injection in Ontario is regulated by both the Ministry <br />of the Environment (MOE) and the Ministry of Natural Resources (MNR). <br />MOE is primarily responsible for wells that dispose of industrial waste <br />and the brine created when caverns are made by dissolution of bedded <br />salt. MNR is primarily responsible for wells that inject oil field <br />brines and fluids used for secondary recovery of hydrocarbons. Over the <br />years, regulatory guidelines adopted by these agencies and their pre- <br />decessors have evolved as problems have occurred and as new knowledge <br />about the properties of the geologic system has been acquired. Regula- <br />tions have been instituted by MOE to control the type of fluid, loca- <br />tion, construction methods, and operating pressures of disposal wells <br />1 <br /> <br />